Interesting topic. I've written only 6 or 7 songs in a period of 11 years. All were for personal expression, enjoyment, and sharing with friends. I find song writing to be very emotionally cleansing and personally rewarding. Even if I were very talented, I would have difficulty writing for financial gain.
With the exception of attending song writing workshops (one by Bob Franke and one by Pat Humphries) where I was expected to (and did) write a song, my song topics, some phrases, and sometimes tunes have jumped out of every day life experiences. Some good and some bad.
For example: Losing my job during the defense industry crash of '88 - '90, caused me to write "The Wall's Come Down". It highlights the conflict of being happy about the new era of world peace (the Berlin Wall came down), with the terrible reality of losing one's job. Leaving beautiful North Branford, CT spawned "Ode To Old North Branford". Leaving Oklahoma (we never left, but we came close) spawned "The Golden Rolling Fields of Oklahoma". I even wrote a rap song (if you know me, you know I'm definately not a rap-type-of-guy) called "Built In Bad Attitude Babe", about a young lady who, when I questioned her perpetual nasty attitude, said she had a built in bad attitude. I shook my head and said, "There has to be a song in here, somewhere". The serenity and wondeful experience of folk music week at Pinewoods brought on "Pinewoods Haunting".
In most of my songs, I have captured (Plagiarized, with credit) a tune, a verse, or a few phrases from one more talented than I.
It's been at least 4 or 5 years since I wrote a song. Nothing exceptionally good or bad has hit me - maybe I should get a life!